It has long been known that absorbent articles such as conventional taped diapers, pull-on diapers, training pants, sanitary napkins, pantiliners, incontinence briefs, and the like, offer the benefit of receiving and containing urine and/or other bodily exudates. To effectively contain exudates, the articles should provide a snug fit around the waist and legs of a wearer. Absorbent articles are known to have a chassis comprising a topsheet, a backsheet, an absorbent core, and barrier and/or gasketing cuffs. Articles such as conventional taped diapers generally include a front and a rear waist section releasably and/or refastenably connected by a fastening system. The fastening system generally comprises an engaging member and a receiving member. The engaging member may be an adhesive tape, a hook bearing tape, or a cohesive tape. The receiving member may be an element or zone on the article that may receive the engaging member such as a polymer film landing zone (viz., for receipt of the adhesive or cohesive tape) or a loop bearing surface (viz., for receipt of the hook bearing tape). The engaging member may be joined to the receiving member thereby interconnecting the rear waist section to the front waist section and thereby forming a waist opening and a pair of leg openings.
Current diaper design frequently includes the use of back ears. Back ears may extend laterally from the longitudinal edge of the rear waist section of the chassis. The engaging member of the fastening system may be attached to the back ear. When the fastening system is engaged, the back ear serves as an interconnecting member between the front waist section and the rear waist section, which together form a waist opening and pair of leg openings. Common back ear construction involves a polymeric material laminated between two substrates. Often back ear construction involves an elastomeric material laminated between two substrates that are supple, soft, and non-irritating to a wearer's skin such as a nonwoven material. Elastomeric films are commonly used since the film provides a degree of stretch to the waist circumference. This stretch allows the diaper to provide a more customized fit. Furthermore, the stretch capability allows the diaper to adjust to the forces exerted by the wearer without causing permanent deformation of the diaper or discomfort for the wearer of the diaper. Elastic back ears are commonly seen in two executions: coterminous and non-coterminous.
Coterminous elastic back ears are back ears where the elastomeric material is substantially coterminous with at least one of the adjoining substrate layers. For example in one commercially available execution, the elastic back ear comprises an elastomeric film between two nonwoven materials. When the back ear is laid flat, the ear has a perimeter. The elastomeric film shares this common perimeter with the nonwoven materials. The problem with coterminous back ears is that elastomeric film is present in locations of the back ear where elastic properties are unnecessary. For example, the back ear may be bonded to the chassis by an adhesive, a pressure bond, or some other bonding technique known in the art. The back ear generally need not exhibit elastic character at points inboard (i.e., closer to the longitudinal centerline of the diaper) of the bond site. As a result, any elastomeric film inboard of the bond site is unnecessary and may represent an added cost to the diaper. Over the course of thousands of diapers produced daily, this added cost without a countervailing consumer benefit can make the diaper unnecessarily expensive. A similar problem may occur where the engaging member is attached to the back ear. The attachment point of the engaging member to the back ear generally prohibits the elastomeric film from stretching. Excess elastomeric film within and outboard of this bond site is unnecessary and may be an added cost.
One way to address the problems present in coterminous elastic back ears is to make the elastomeric material non-coterminous. A non-coterminous back ear has an elastomeric material that does not fully overlap the ear. For example, in one commercially available execution, the back ear comprises an elastomeric film between two nonwoven materials. The back ear has two opposing and substantially parallel edges; one edge being proximate to the rear waist region of the chassis and the other edge being proximate to the engaging member. The elastomeric film has edges that run parallel to but do not share the same edge as the two opposing back ear edges. This results in two void regions in the back ear. The void region is an area of the ear in which no elastomeric film is present. The void region may comprise another substrate such as one or more layers of a nonwoven material. One void region may serve as the bonding location for the back ear to the chassis and the other void region may serve as the bonding location for the engaging member of the fastening system to the back ear. While the non-coterminous back ears improve cost-efficiency of the diaper by reducing unnecessary elastomeric film, these ears can have deficiencies.
One common problem of non-coterminous (as well as conterminous) ears is with regard to joining the ear to the chassis. Back ears are often joined to the chassis by one or more bonding techniques. For example, during manufacture, an adhesive may be applied to the chassis and then the back ear is applied thereto. One problem with the use of adhesive to join the back ear to the chassis relates to over-application. The adhesive is often applied adjacent to the longitudinal edge of the chassis. This proximity to the longitudinal edge can result in adhesive being applied beyond the edge of the chassis, which results in wasted adhesive and increases the manufacturing costs of the article. Furthermore, adhesive overspray can contaminate the process line thereby increasing defects and prompting more frequent line stoppages.
Another problem related to adhesive bonding involves the strength of the adhesive bond. As described above, the back ear generally comprises an elastomeric film between two nonwoven materials. Likewise, the outermost and innermost planar surfaces of the chassis are typically nonwoven materials (i.e., a nonwoven outer cover or a nonwoven topsheet). By adhesively joining the back ear to the chassis, the adhesive is effectively engaging and joining two nonwoven materials (i.e., the nonwoven of the back ear and the nonwoven of the chassis). An adhesive bond between two nonwovens may lack the tensile strength necessary for the back ear, which is subjected to elongating forces when the diaper is applied. To further strengthen the connection of the back ear and the chassis, mechanicals bonds are frequently used.
A variety of mechanical bonding techniques are known in the art. One such technique is pressure bonding, which involves applying high pressure at a bond site to compress the materials to be joined. Particularly with polymeric materials, the pressure may heat the materials enabling them to flow together. Upon cooling, the materials may be fused together and/or may fuse together around the perimeter of the bond site. A plurality of bond sites are typically created and may be arranged in a substantially linear arrangement. While pressure bonding can increase the bond strength between the back ear and the chassis, an unintended consequence of pressure bonding may be weakening of the nonwoven proximate to the bond sites. This weakening is particularly evident when the pressure bonding occurs within the void region of the back ear. Since the pressure bonds may cause the nonwoven material of the void region to flow, the bond sites can serve as perforations in the nonwoven. When a strain is applied to the back ear such as during application of the diaper, the nonwoven is prone to tearing along the bond sites. Such tearing is viewed as highly undesirable since the diaper fails prior to use.
Accordingly, it would be desirable to provide an absorbent article having a front and/or back ear that eliminates the excessive and unnecessary elastomeric material of the coterminous back ears while addressing the bonding issues present in the non-coterminous back ears having a void region.